CVE-2025-63649
📋 TL;DR
This vulnerability allows attackers to cause a Denial of Service (DoS) by sending a specially crafted POST request to the Monkey web server. The out-of-bounds read in the HTTP parser can crash the server, disrupting service availability. Any system running vulnerable versions of Monkey web server is affected.
💻 Affected Systems
- Monkey web server
⚠️ Risk & Real-World Impact
Worst Case
Complete service disruption with server crash requiring manual restart, potentially leading to extended downtime.
Likely Case
Server crash and service interruption until the process is restarted, causing temporary DoS.
If Mitigated
Limited impact with proper network segmentation and monitoring allowing quick detection and response.
🎯 Exploit Status
Exploitation requires sending a crafted HTTP request, which is straightforward for attackers.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Versions after commit f37e984
Vendor Advisory: https://github.com/archersec/security-advisories/blob/master/monkey/monkey-advisory-2025.md
Restart Required: Yes
Instructions:
1. Update Monkey to a version after commit f37e984. 2. Rebuild from source if using custom builds. 3. Restart the Monkey service.
🔧 Temporary Workarounds
Block chunked transfer encoding
allConfigure web application firewall or reverse proxy to block or sanitize requests with chunked transfer encoding.
Rate limiting
allImplement rate limiting on POST requests to reduce impact of DoS attempts.
🧯 If You Can't Patch
- Implement network segmentation to isolate Monkey servers from untrusted networks.
- Deploy intrusion detection systems to monitor for crafted POST requests and alert on suspicious activity.
🔍 How to Verify
Check if Vulnerable:
Check Monkey version or commit hash against vulnerable range (up to f37e984).Check Version:
monkey --version or check the source commit hash if built from source.Verify Fix Applied:
Verify the installed version is after commit f37e984 and test with a crafted POST request (in a controlled environment).📡 Detection & Monitoring
Log Indicators:
- Server crash logs
- Unexpected termination of Monkey process
- Error messages related to HTTP parsing
Network Indicators:
- Multiple POST requests with unusual chunked encoding patterns
- Requests causing server non-responses
SIEM Query:
source="monkey.log" AND ("crash" OR "segfault" OR "http_parser")